The present invention comprises a new and distinct cultivar of Prunus hybrid used as a rootstock known by the varietal name ‘Gi31817’. The new variety was discovered in Giessen, Germany in 1970. The new variety is the result of a planned breeding program between an unnamed Prunus canescens variety (female parent) and a mixture of pollen as the male parentage from several unnamed and presumably unpatented varieties of Prunus avium. The new variety has larger leaves, less leaf pubescence, stronger vigor, and induces stronger vigor of a grafted tree than its female parent. When compared to the varieties making up its male parentage, the new variety does not grow as upright and also induces less growth and higher precocity of a grafted tree. The purpose of the breeding program was to produce a series of size-controlling, productive, and precocious rootstocks for sweet cherries. The new variety has been trial and field tested and has been found to retain its distinctive characteristics and remain true to type through successive propagations.
The new variety is similar to prunus rootstock ‘GI 148/2’ (U.S. Plant Pat. No. 9,622) in its rootstock induction of precosity, rootstock induction of flat branching, and the absence of root suckers. The leaves of the new variety have a different appearance than those of ‘GI 148/2’. Further, the vigor of a grafted tree on the new variety is much greater than on ‘GI 148/2’.